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Li, Peng

Publications and source records attributed to Li, Peng.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Single-atom tailoring of platinum nanocatalysts for high-performance multifunctional electrocatalysis

Platinum-based nanocatalysts play a crucial role in various electrocatalytic systems that are important for renewable, clean energy conversion, storage and utilization. However, the scarcity and high cost of Pt seriously limit the practical application of these catalysts. Decorating Pt catalysts with other transition metals offers an effective pathway to tailor their catalytic properties, but often at the sacrifice of the electrochemical active surface area (ECSA). Here we report a single-atom tailoring strategy to boost the activity of Pt nanocatalysts with minimal loss in surface active sites. By starting with PtNi alloy nanowires and using a partial electrochemical dealloying approach, we create single-nickel-atom-modified Pt nanowires with an optimum combination of specific activity and ECSA for the hydrogen evolution, methanol oxidation and ethanol oxidation reactions. The single-atom tailoring approach offers an effective strategy to optimize the activity of surface Pt atoms and enhance the mass activity for diverse reactions, opening a general pathway to the design of highly efficient and durable precious metal-based catalysts.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Stabilization of Formate Dehydrogenase in a Metal–Organic Framework for Bioelectrocatalytic Reduction of CO 2

Abstract The efficient fixation of excess CO 2 from the atmosphere to yield value‐added chemicals remains crucial in response to the increasing levels of carbon emission. Coupling enzymatic reactions with electrochemical regeneration of cofactors is a promising technique for fixing CO 2 , while producing biomass which can be further transformed into biofuels. Herein, a bioelectrocatalytic system was established by depositing crystallites of a mesoporous metal–organic framework (MOF), termed NU‐1006, containing formate dehydrogenase, on a fluorine‐doped tin oxide glass electrode modified with Cp*Rh(2,2′‐bipyridyl‐5,5′‐dicarboxylic acid)Cl 2 complex. This system converts CO 2 into formic acid at a rate of 79±3.4 m m h −1 with electrochemical regeneration of the nicotinamide adenine dinucleotide cofactor. The MOF–enzyme composite exhibited significantly higher catalyst stability when subjected to non‐native conditions compared to the free enzyme, doubling the formic acid yield.

Chen, Yijing↗
DOE OSTI2019

Toward Design Rules of Metal–Organic Frameworks for Adsorption Cooling: Effect of Topology on the Ethanol Working Capacity

Using combined experimental and computational approaches, we studied the adsorption behavior of ethanol in a series of metal-organic frameworks (MOFs) with similar building blocks but different topologies and tested their performance as adsorption coolers. Here, we analyzed the relationship between the MOF structures and their ethanol working capacities under different working conditions. Molecular-level insights into the microscopic adsorption behavior were also gained from atomistic simulations. Based on the structure-property relationships that we found, we selected another MOF (MOF-525) for study, and our experiments and simulations both showed superior ethanol working capacity for this MOF, which verified our design rules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Synthetic Control of Thorium Polyoxo-Clusters in Metal–Organic Frameworks toward New Thorium-Based Materials

Control over the assembly of thorium-based polyoxo-clusters remains a great challenge because of their quick olation and oxolation reactions. Here, we report the synthesis and isolation of two pure phase thorium polyoxocluster-based metal-organic frameworks (Th-MOFs), ThNU-1008 and Th-NU-1011. Crystal structures of these ThMOFs reveal two distinct 8-connected polyoxo-clusters: a hexanuclear cluster [Th 6 (μ 3 -O) 4 (OH) 4 (H 2 O) 6 (HCOO) 4 ] was observed in Th-NU-1008 and a tetranuclear cluster [Th 4 (μ 3 -) 2 (OH) 4 (DMF) 2 (H 2 O) 4 ] in Th-NU-1011 which has never been reported before among thorium species. In both Th-NU-1008 and Th-NU-1011, the tetratopic linker, 1,4-dibromo-2,3,5,6-tetrakis(4-carboxyphenyl) benzene, joins the clusters together, forming two three-periodic networks, each with csq topology. The Brunauer-Emmett-Teller (BET) surface areas calculated from the Ar isotherms are approximately 800 and 700 m 2 g -1 for Th-NU-1008 and Th-NU-1011, respectively. Because the linkers are oriented orthogonal to each other in the two respective MOFs, a 32 Å hexagonal channel is observed in Th-NU-1008 while a 15 Å channel is observed in Th-NU-1011. This work opens a new avenue to construct unexplored Th-MOF materials with targeted polyoxo-cluster structures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Successful Decontamination of 99 TcO 4 - in Groundwater at Legacy Nuclear Sites by a Cationic Metal-Organic Framework with Hydrophobic Pockets

99 Tc contamination at legacy nuclear sites is a serious and unsolved environmental issue. The selective remediation of 99 TcO 4 - in the presence of a large excess of NO 3 - and SO 4 2- from natural waste systems represents a significant scientific and technical challenge, since anions with a higher charge density are often preferentially sorbed by traditional anion exchange materials. We present a solution to this challenge based on a stable cationic metal-organic framework, SCU-102 (Ni 2 (tipm) 3 (NO 3 ) 4 ), which exhibits fast sorption kinetics, a large capacity (291 mg g 1 ), a high distribution coefficient, and, most importantly, a record-high TcO 4 - uptake selectivity. This material can almost quantitatively remove TcO 4 - in the presence of a large excess of NO 3 - and SO 4 2- . Finally, decontamination experiments confirm that SCU-102 represents the optimal Tc scavenger with the highest reported clean-up efficiency, while first-principle simulations reveal that the origin of the selectivity is the recognition of TcO 4 - by the hydrophobic pockets of the structure.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Stabilization of an Unprecedented Hexanuclear Secondary Building Unit in a Thorium-Based Metal–Organic Framework

The crystal structures of thorium clusters are important for understanding the formation and transformation mechanisms of actinide species in solution, which can in turns benefit nuclear waste processing and management. However, stabilizing thorium clusters in aqueous solution is quite challenging because of their fast olation and oxolation reactions. Here, we report a thorium-based meta-organic framework, NU-905, with the formula [Th 6 (μ 3 -O) 2 (HCOO) 4 (H 2 O) 6 ] [TCPP = tetrakis(4-carboxyphenyl)porphyrin], synthesized by a solvothermal reaction in N,N-dimethylformamide and water at 120 °C. NU-905 contains a hexanuclear secondary building unit (SBU), [Th 6 (μ 3 -O) 2 (HCOO) 4 (H 2 O) 6 ], which has never been reported previously. The SBUs are capped and bridged by the tetratopic linker TCPP to form a three-dimensional network with scu topology. The activated NU-905 exhibits permanent porosity and shows high catalytic activity for the selective photooxidation of a mustard gas simulant.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

A Bismuth Metal–Organic Framework as a Contrast Agent for X-ray Computed Tomography

A new bismuth metal–organic framework (MOF), bismuth-NU901 (Bi-NU-901), featuring the scu topology and a pore with a diameter of ~11 Å, was solvothermally synthesized, and its use as an X-ray computed tomography (CT) contrast agent was tested. X-ray CT is a common diagnostic method used in the medical field. Inside the body, contrast media enhance the distinction between tissues and organs of similar density. Bi-NU-901 consists of eight connected Bi 6 nodes and tetratopic 1,3,5,8-( p -benzoate)pyrene linkers (TBAPy). Numerous material characterization studies including powder X-ray diffraction (PXRD), scanning transmission electron microscopy (STEM), and DFT pore size distribution support the scu structure. Additionally, given the framework’s high density of nontoxic heavy atoms, Bi-NU-901 was evaluated as an X-ray computed tomography (CT) agent. Importantly, in vitro studies revealed this new bismuth MOF demonstrates p7 times better contrast intensity compared to a zirconium MOF featuring the same topology and ~14 times better contrast than a commercially available CT contrast agent. Furthermore these results suggest bismuth MOFs may be promising CT contrast agents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Probing the origin of extreme magnetoresistance in Pr/Sm mono-antimonides/bismuthides

Combining angle-resolved photoemission spectroscopy and magnetotransport measurements, we systematically investigated the possible origin of the extreme magnetoresistance in Pr/Sm mono-antimonides/bismuthides (PrSb, SmSb, PrBi, SmBi). Our photoemission measurements reveal that the bulk band inversion and surface states are absent (present) in Pr/Sm antimonides (bismuthides), implying that topological surface states are unlikely to play an important role for the observed extreme magnetoresistance. We found that the electron- hole compensation is well satisfied in all these compounds and the bulk band structure exhibits no obvious temperature dependence from 10 up to 150 K. Simultaneous fittings of the magnetoresistance and Hall coefficient reveal that the carrier mobility is dramatically enhanced at low temperature, which naturally explains the suppression of extreme magnetoresistance at high temperatures. Our results therefore show that the extreme magnetoresistance in these compounds can be well accounted for by the two-band model with good electron-hole compensation. Lastly, we found that both PrSb and SmSb exhibit highly linear bulk bands near the X point and lie close to the transition point between a topologically trivial and nontrivial phase, which might be relevant for the observed anomalous quantum oscillations.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Interpenetration Isomerism in Triptycene‐Based Hydrogen‐Bonded Organic Frameworks

Abstract We describe an example of “interpenetration isomerism” in three‐dimensional hydrogen‐bonded organic frameworks. By exploiting the crystallization conditions for a peripherally extended triptycene H 6 PET, we can modulate the interpenetration of the assembled frameworks, yielding a two‐fold interpenetrated structure PETHOF‐ 1 and a five‐fold interpenetrated structure PETHOF‐ 2 as interpenetration isomers. In PETHOF‐ 1 , two individual nets are related by inversion symmetry and form an interwoven topology with a large guest‐accessible volume of about 80 %. In PETHOF‐ 2 , five individual nets are related by translational symmetry and are stacked in an alternating fashion. The activated materials show permanent porosity with Brunauer‐Emmett‐Teller surface areas exceeding 1100 m 2 g −1 . Synthetic control over the framework interpenetration could serve as a new strategy to construct complex supramolecular architectures from simple organic building blocks.

Li, Penghao↗
DOE OSTI2018

“Interpenetration Isomerism” of Triptycene-Based Hydrogen-Bonded Organic Frameworks

In this work, we describe an example of “interpenetration isomerism” in three-dimensional (3D) hydrogen-bonded organic frameworks (HOFs). By exploiting the crystallization conditions for a peripherally extended triptycene H6PET, we can modulate the interpenetration of the assembled frameworks, yielding a two-fold interpenetrated structure PETHOF-1 (acs-2c topology) and a five-fold interpenetrated structure PETHOF-2 (acs-5c topology) as “interpenetration isomers”. In PETHOF-1, two individual nets are related by inversion symmetry and form an interwoven topology with a strikingly large guest-accessible volume of about 80%. In PETHOF-2, five individual nets are related by translational symmetry and are stacked in an alternating fashion. Additionally, the activated materials show permanent porosity with high Brunauer–Emmett–Teller (BET) areas exceeding 1100 m2•g-1. Finally, we believe that synthetic control over the framework interpenetration can serve as a new design strategy to construct diverse and complex supramolecular architectures from simple organic building blocks.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Versatile Ligand-Exchange Method for the Synthesis of Water-Soluble Monodisperse AuAg Nanoclusters for Cancer Therapy

A general-applicable two-phase ligand exchange method is developed to prepare a series of monodisperse water-soluble AuAg nanoclusters. This method relies on the ligand exchange of the water-soluble ligands (e.g., tiopronin, captopril, N-acetyl-l-cysteine, 4-mercaptobenzoic acid, glutathione, and mercaptosuccinic acid) with phenylacetylene and triphenylphosphine co-protected AuAg precursors. Both polyacrylamide gel electrophoresis (PAGE) and transmission electron microscopy (TEM) indicate the monodispersity and ultrasmall size of the prepared water-soluble metal nanoclusters. In addition, the structure has also been characterized by UV–vis absorption spectroscopy, extended X-ray absorption fine structure (EXAFS), electrospray ionization time-of-flight mass spectra (ESI-TOF-MS), etc. The preliminary application of the as-prepared AuAg nanoclusters protected with tiopronin has been explored via the postmodification of the carboxyl groups of thiols with doxorubicin (DOX).

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Study on the Extraction of Aluminum From Aluminum Dross Using Alkali Roasting and Subsequent Synthesis of Mesoporous γ-Alumina

This study presents a process for recovering aluminum from aluminum dross (an industrial waste product) via an alkali roasting process and using it to synthesize mesoporous γ-alumina. The results show that the inherent chlorides in dross (KCl and NaCl) reduce Al extraction efficiency and should be removed first by water leaching. Use of salt-free dross increases the Al extraction rate (from 85 to 96 pct) within 90 minutes alkali roasting at 923 K (650 °C). In addition, an ammonium bicarbonate byproduct can be obtained from water leaching due to the hydrolysis of AlN, which can be used as a precipitating agent in the boehmite sol preparation. Synthesis of mesoporous γ-alumina was carried out by the sol-gel method with EO{sub 20}PO{sub 70}EO{sub 20} (P123) as a template. The prepared mesoporous γ-alumina was characterized as having a disordered mesostructure with a high pore volume of 1.02 cm{sup 3}/g and surface area of 312 m{sup 2}/g. Thus, we achieved highly efficient utilization of aluminum dross and yielded products with high added value. Mesoporous γ-alumina has potential applications in environmental remediation and catalysis.

36 MATERIALS SCIENCE↗
DOE OSTI2018

From Transition Metals to Lanthanides to Actinides: Metal-Mediated Tuning of Electronic Properties of Isostructural Metal–Organic Frameworks

In this study, isostructural metal-organic frameworks (MOFs) have been prepared from a variety of metal-oxide clusters, including transition metals, lanthanides, and actinides. Experimental and calculated shifts in O–H stretching frequencies for hydroxyl groups associated with the metal-oxide nodes reveal varying electronic properties for these units, thereby offering opportunities to tune support effects for other materials deposited onto these nodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Pulse MIG Welding of 6061-T6/A356-T6 Aluminum Alloy Dissimilar T-joint

Dissimilar T-joints between 4-mm-thick wrought 6061-T6 and cast A356-T6 aluminum alloy plates are made with pulse metal inert gas welding (P-MIG) process, and the weld geometry, microstructure and mechanical properties of the joints are investigated. The average tensile load of the joints is 9488 N at travel speed 12 mm/s and welding current 165 A with 6061 aluminum alloy as web plate and A356 aluminum alloy as flange plate. The weld zone (WZ) is composed of dendrite zone and columnar zone, which is wide at bottom of weld making it become a weak zone. Besides, grain boundary (GB) liquation, consisting of GB eutectic and solute-depleted α-Al, occurs in the partially melted zone on 6061 aluminum alloy side. The T-joint with highest tensile load fails at the root of WZ and the flange plate near the weld with different fracture modes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

MicroRNA-30c-5p inhibits NLRP3 inflammasome-mediated endothelial cell pyroptosis through FOXO3 down-regulation in atherosclerosis

Highlights: • Addition of miR-30c-5p inhibited ox-LDL-induced pyroptosis in HAECs. • NLRP3 inflammasome was associated with miR-30c-5p-mediated HEACs pyroptosis. • FOXO3 was a target of miR-30c-5p. • Silencing of FOXO3 attenuated anti-miR-30c-5p-mediated HAECs pyroptosis. Atherosclerosis is a chronic inflammatory disease involved in endothelial dysfunction. Pyroptosis is a pro-inflammatory form of cell death and plays pivotal roles in atherosclerosis. MicroRNAs (miRNAs) are implicated in atherosclerosis, however the mechanisms that underlie miR-30c-5p is required for endothelial cell pyroptosis remain elusive. In the present study, we probed the interaction of miR-30c-5p with forkhead box O3 (FOXO3) and investigated the effect of miR-30c-5p and FOXO3 on NLRP3 inflammasome and endothelial cell pyroptosis. Introduction of oxidized low density lipoprotein (ox-LDL) dose-dependently increased lactate dehydrogenase (LDH) release as well as pyroptosis in human aortic endothelial cells (HAECs). On the basis of ox-LDL treatment, we found the expression of miR-30c-5p was impaired and enrichment of miR-30c-5p protected HAECs from ox-LDL-induced pyroptosis. Moreover, addition of miR-30c-5p inhibited ox-LDL-activated NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, which was associated with HEACs pyroptosis. Nevertheless, miR-30c-5p failed to show efficacy of Toll-like receptor (TLR) signaling of NLRP3 inflammasome activation. Intriguingly, FOXO3 was suggested to be targeted by miR-30c-5p and addition of miR-30c-5p blocked FOXO3 expression, whereas miR-30c-5p depletion showed opposite effects. Furthermore, silencing of FOXO3 inhibited NLRP3-mediated pyroptosis and reversed anti-miR-30c-5p-induced activation of NLRP3 inflammasome and pyroptosis in HEACs with ox-LDL treatment. Our finding suggested that miR-30c-5p might play essential role in NLRP3 inflammasome-modulated cell pyroptosis by targeting FOXO3 in HAECs, providing a novel therapeutic avenue for atherosclerosis treatment.

60 APPLIED LIFE SCIENCES↗